Glucose-6-phosphate Dehydrogenase and Aldolase in Lenses of Lactose-fed Rats

IT has been shown that in lenses of galactose-fed rats there is a decrease of glucose-6-phosphate dehydrogenase1,2 and aldolase3. These findings support the statement that there is an interference of glucose metabolism in the lens during the development of galactose cataracts. In the previous experiments2 glutathione reductase was also determined as a coupled system with the glucose-6-phosphate dehydrogenase through the utilization of the oxidized and reduced forms of nicotinamide-adenine dinucleotide phosphate (NADP). The activity of the glutathione reductase was reduced similarly to the glucose-6-phosphate dehydrogenase. Incubation of normal lens homogenate with galactose or galactose-1-phosphate showed no inhibitory effect on the glucose-6-phosphate dehydrogenase or aldolase activities2,3. Considering these results, and also that a lowered amount of soluble proteins per mg lens was found in the lactose-fed rats3, we came to the conclusion that this was due to a decreased protein synthesis in lenses in this condition. However, aldolase was more affected than glucose 6-phosphate dehydrogenase, which may indicate a more direct action on the glycolytic pathway, which is, quantitatively, the most important pathway of glucose metabolism in lens4. The former experiments were performed independently with two different sets of rats. In order to know which of the two pathways is affected first, another group of animals was examined.